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• FFMpeg Speed up transparent webm C#/Cmd

  17 avril 2023, par Alphapixel 182004

  I am trying to speed up a webm video file while maintaining the transparency but every attempt I've made has removed the transparency.

  


  How do I speed up a transparent webm using FFMpeg without losing the transparency ?

  


  Note : I am doing this all in c# but would prefer to use commands instead of wrapper libraries.

  


  this is the general command I have tried :

  


  command = $"-i \"{input}\" -filter_complex \"[0:v]setpts = (1/{speed}) * PTS[v]; [0:a]atempo = {speed}[a]\" -map \"[v]\" -map \"[a]\" -c:v libvpx-vp9 -b:v 1M -y \"{output}";
That command did not maintain transparency though.

  


  A little info about the input video :

  


  


  • The input is transparent

    


  


  • the input is basically a mess of individual transparent webm's joined together that were made with either :

    


    

    • Poster with audio :

    


    


  


  


  $"-threads 4 -loop 1 -i \"{image}\" -i \"{audio}\" -c:v libvpx-vp9 -pix_fmt yuva420p -crf 10 -b:v 0 -c:a libopus -b:a 192k -shortest -movflags +faststart -y \"{output}\"";

  


  

  • Padding the clip :

  


  


  $"-i \"{input}\" -filter_complex \"[0:v]split=2[v1][v2];[v1]tpad=start_duration={startPadMs / 1000}:start_mode=clone:stop_duration={endPadMs / 1000}:stop_mode=clone[v1_edited];[v1_edited][v2]overlay=eof_action=pass[v];[0:a]adelay={startPadMs}|{startPadMs}[a]\" -map \"[v]\" -map \"[a]\" \"{output}\""

  


  

  • Joining videos :

  


  


  var temp = Path.Combine(Path.GetTempPath(), "concat.txt"); File.WriteAllText(temp, string.Join('\n', clips.Select(e => $"file '{e}'"))); var command = $"-f concat -safe 0 -i "{temp}" -c copy -y "{output}"";\

  


• lavu : add an API function to return the FFmpeg version string

  30 juin 2015, par wm4

  lavu : add an API function to return the FFmpeg version string
  This returns something like "N-73264-gb54ac84". This is much more useful
  
  than the individual library versions, of which there are too much and
  
  which are very hard to map back to releases or git commits.
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] doc/APIchanges
  • [DH] libavutil/avutil.h
  • [DH] libavutil/utils.c

• How to use ffmpeg for live streaming fragmented mp4 ?

  2 mai 2018, par Cross_

  Following a variety of stackoverflow suggestions I am able to create a fragmented MP4 file, then slice it into the header part (FTYP & MOOV) and various segment files (each containing MOOF & MDAT). Using Media Source Extensions I download and add the individual segments - that’s all working great.

  Now I would like to create a live streaming webcam with that same approach. I had hoped that I could just send the MOOV box to each new client plus the currently streaming segment. This however is rejected as invalid data in the browser. I have to start with the first segment and they have to be appended in order. That’s not helpful for a live streaming scenario where you don’t want to see the whole stream from the start. Is there any way to alter the files so that the segments are truly independent and you can start playback from the middle ?

  For reference, this is how I am setting up the stream on the OS X server :

  $ ffmpeg -y -hide_banner -f avfoundation -r 30 -s 1280x720
  -pixel_format yuyv422 -i default -an -c:v libx264 -profile:v main -level 3.2 -preset medium -tune zerolatency -flags +cgop+low_delay -movflags empty_moov+omit_tfhd_offset+frag_keyframe+default_base_moof+isml
  -pix_fmt yuv420p | split_into_segments.py

  Playback is done with a slightly modified version of this sample code :
  https://github.com/bitmovin/mse-demo/blob/master/index.html